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Former Beacon Station No. 12474 March 18,2002 <br /> Stockton California Problem Assessment Report/Corrective Action Plan <br /> 8.2.1 Passive Remediation <br /> Passive remediation involves monitoring of groundwater to evaluate the progress of natural <br /> bio-degradation, volatilization, or dispersion of petroleum hydrocarbons. The effectiveness <br /> of passive remediation is indicated by a decrease in petroleum hydrocarbon concentrations in <br /> groundwater through time. <br /> 8.2.1 Aboveground Treatment <br /> This remediation alternative typically involves .the extraction, treatment, and disposal of <br /> groundwater. Groundwater extraction wells, or interceptor trenching if shallow groundwater <br /> is present, may be used for groundwater removal. Removal of petroleum hydrocarbons from <br /> the extracted groundwater may utilize product/water separation, air-stripping of volatile <br /> constituents, activated carbon absorption, bio-treatment, or ultraviolet light degradation. <br /> After treatment, groundwater may be discharged to the storm or sanitary sewer system, <br /> depending on local discharge regulations. <br /> 8.2.2 Air Sparging <br /> Air sparging involves the injection of pressurized air into the saturated zone to facilitate <br /> migration of volatile constituents from groundwater into the vadose zone where they can be <br /> removed by soil vapor extraction. The injected air migrates horizontally and vertically in the <br /> saturated soil creating transient air-filled regimes in which volatile compounds enter into the <br /> gas phase and are carried by air movement into the vadose zone. This alternative may <br /> extend the utility of soil vapor extraction to water-saturated soils. An additional benefit to <br /> air sparging is the introduction of oxygen into the groundwater, which stimulates natural <br /> biodegradation. <br /> • <br /> 474PARCAP3-02.doc 16 <br /> Project No. 1474.23 HORIZON ENVIRONMENTAL INC. <br />